13.12 Histology: Liver and Pancreas Flashcards
What is the liver derived from?
Endoderm
How many surfaces does a hepatocyte have and how wide is it across?
Polyhedral, 25um across
How many nuclei and how many copies of DNA do hepatocytes have?
1-2 nuclei
tetraploid or polyploid
What structures do hepatocytes contain (and how do these reflect their purpose)?
Rough ER, golgi, secretory vesicles (PRO synthesis)
Prominent smooth ER (FAT metabolism)
Many mitochondria
What type of cells are hepatocytes?
Epithelial cells (replaced regularly by division of existing hepatocytes)
Hepatocytes comprise ___% of liver weight
75%
What are the blood supplies for the liver?
Majority, venous blood from gut (hepatic portal system)
Also arterial supply
What surrounds the liver?
A thin capsule (Glisson’s capsule)
What fibres are the hepatocytes supported by?
Reticular fibres (collagen type III)
How are hepatocytes organised?
Into lobules (stacks of hepatocytes in plates)
How does blood flow into the liver?
Into lobule, then across to central vein (outside in)
What is the portal triad comprised of?
Hepatic portal vein (deoxygenated blood from gut), hepatic artery and bile duct
Where do sinusoids converge?
On the central vein (carrying blood to hepatic vein and out of liver)
What is a sinusoid?
A network that veins and arteries give rise to that carry blood to plates of hepatocytes
What is the Space of Disse?
A place where the hepatocytes are directly bathed by plasma (too small for cells)
How is a hepatic acinus organised?
Zone 1: best O2 supply
Zone 2
Zone 3: worst O2 supply (closest to central vein)
Which zone’s hepatocytes are the first to die if there are toxins or metabolites?
Toxin: Zone 1 dies
Metabolites: Zone 3 dies (low concentration of nutrients)
What are the differences in the three zones in hepatic acini?
Zone 1: high in O2, toxins, nutrients
Zone 3: low in O2, toxins, nutrients
How is bile produced?
Hepatocytes (bile salts from cholesterol)
Which direction does bile flow in the liver?
Outwards (collected into ducts)-opposite direction to blood
How is bile reabsorbed?
In the small intestine (concentrates bile salts and pigments), approx 90%
How does the gall bladder know when to contract to secrete bile?
Fat–>CCK into blood–>gall bladder contracts–>relaxation of sphincter of Oddi–>squirt of bile into duodenum
Where do the ducts draining the pancreas join the common bile duct?
At the sphincter of Oddi
Why doesn’t the pancreas digest itself?
Zymogen enzymes are secreted in an inactive form and activate upon hitting bile/other enzymes
